Checking the file size before submitting the form has always been like a forbidden fruit to us, that’s because there was no easy way to access clients’ file system, which can return the exact size of a file before sending it to the server. Old browsers have no inbuilt capability, and Javascript won’t do it, so normally people would use flash to calculate the file size in HTML upload forms, and most of us just preferred to skip the client part, letting server handle the problem.
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